Tarnished Plant Bug. Populations of tarnished plant bugs were collected from wild hosts in cotton growing areas of West Tennessee and sent to Xx. Xxxxxx Xxxxxxxxx (USDA ARS, Stoneville, MS). As part of a regional effort, scientists from Mississippi and Arkansas also submitted samples. Indeed, Tennessee scientists assisted in collecting four populations from northern Arkansas. However, only data for Tennessee (2006-2008) are shown. Three classes of insecticides were evaluated including synthetic pyrethroids (permethrin) and organophosphates (Monitor or acephate). If sufficient numbers of insects were collected, assays with neonicotinoid insecticides (imidacloprid or thiamethoxam) were done to generate baseline susceptibility data to this class of insecticides. The results of insecticide treated vial assays for each population are presented, and populations were considered at least moderately resistant if: • permethrin or Monitor --- discriminating dose mortality < 75%, or • acephate --- LC50 Value > 7.50
Tarnished Plant Bug. Data from Tennessee (below) indicated relatively low levels of resistance compared with the lower mid-southern states, particularly Mississippi and Louisiana. However, survival in assays using acephate indicated all populations had at least moderate levels of resistance to this insecticide. The same was true for populations collected for northern Arkansas. A trend toward decreasing susceptibility to acephate appears to be occurring, but thus far, obvious field control failures have not been observed in Tennessee. No populations showed significant levels of resistance to permethrin, indicating that pyrethroids should still provide adequate plant bug control in cotton if populations are not unusually high. No resistance issues have been identified for neonicotinoid insecticides (imidacloprid or thiamethoxam) indicating that Trimax Pro and Centric should provide control of tarnished plant bugs similar to that observed in previous years. Tarnished plant bug insecticide assay data from Tennessee from 2006 - 2008. Bolded numbers indicate populations with potential resistance. Year Collection Site (County) Discriminating Dose (% Mortality) LC50 Value (ug) Monitor Permethrin Acephate Imidacloprid 2006 Xxxxxxx* 86 100 --- 0.81 Lauderdale* 90 100 --- 0.86 Madison* 98 100 --- 0.71 Xxxxxx* 98 100 --- 0.93 Xxxxxxxx 60 86 4.92 --- Xxxx 86 68 --- 2.21 2007 Xxxxxxx* 72 98 7.22 --- Lake* 88 75 --- --- Madison* 68 96 9.62 --- Xxxx 96 96 10.53 1.04 Xxxxxxxx 90 100 4.89 --- Xxxxxx 88 84 10.64 --- 2008 Xxxxxxxx --- 86 11.03 --- Lauderdale --- 96 --- --- Madison --- 96 7.82 --- Xxxxxx --- 86 9.43 1.13** * Spring or early summer samples (other samples were made late summer or early fall). ** Thiamethoxam (i.e., Centric) used in this assay.
